1991 Isuzu Impulse RSFACTORY OEM SERVICE PROCEDURE

Ignition Timing

  1. With transmission in Neutral or Park, start engine and warm to normal operating temperature. Ensure CHECK ENGINE light is off. Turn engine and all accessories off.
  2. Connect jumper wire between ALDL diagnostic connector terminals No. 1 and 3. ALDL connector is White 3-pin connector, located behind right side of instrument panel. See Fig 1 . Connect timing light to No. 1 spark plug wire. Start engine.
    Fig 1: Locating ALDL Diagnostic Connector
    G90D14939Courtesy of ISUZU MOTOR CO.
  3. Check ignition timing. See IGNITION TIMING specification table. Increase engine speed to 1500-2000 RPM to read timing (if necessary).
  4. Adjust timing by loosening distributor hold-down bolt and turning distributor. Tighten distributor hold-down bolt to 17 ft. lbs. (24 N.m). Recheck timing. Remove jumper wire from ALDL connector and ensure CHECK ENGINE light is off. Idle speed is automatically controlled by ECM.
IGNITION TIMING (Degrees BTDC@RPM)

Application Base Timing
1.6 (1) 9-11
(1) With jumper wire installed in ALDL diagnostic connector, located behind right side of instrument panel. Increase engine speed to 1500-2000 RPM to read timing (if necessary).
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.